Field of the Invention
The present invention relates to an improvement of a differential device which distributively transmits rotational force of an input member to a pair of mutually-independent output shafts, the input member retaining a pinion support portion that supports a pinion and being rotatable together with the pinion support portion. Particularly, the present invention relates to an improvement of the differential device that includes: a pair of side gears each having an outer peripheral portion which includes an annular toothing portion in mesh with the pinion and connected to the pair of output shafts, respectively; and a cover portion covering an outside of at least one side gear and rotating integrally with the input member.
Description of the Related Art
Conventionally, such a differential device is widely known as disclosed in, for example, Japanese Patent No. 4803871 and Japanese Patent Application KOKAI Publication No. 2002-364728.
The design of a differential device has been desired to be improved such that each of the side gears can have a sufficiently large diameter to have a sufficiently larger number of teeth than the number of teeth of each pinion, and that the side gears and the cover portions arranged outside of the side gears can be reduced in thickness in the axial direction of the output shafts. However, the conventional differential device has not been improved sufficiently in the aforementioned points, and the differential device itself still has a structural form relatively wide in the axial direction of the output shafts. This may cause undesirable things such as: difficulty in incorporating the differential device in a transmission system under many layout restrictions around the differential device; increase in the size of the transmission system as a whole due to the incorporation of the differential device therein; and the like.
In addition, if the thickness of the cover portions is merely reduced in order to flatten the differential device in the axial direction, the cover portions are structurally prone to tilt in a thrust direction. Even a slight tilt of the cover portions may cause problems such as: deterioration in meshing accuracy of an input toothing portion (a final driven gear) fixed to an outer periphery of the input member; occurrence of unusual noises; and the like. Moreover, if a structural object adjacent to the differential device applies force in the thrust direction to the cover portions which are not thick enough, the cover portions may press component parts inside the cover portions and adversely affect the meshing accuracy of the side gears with the pinions as well.